


Sigmate | AtsuOiHina Omegaverse AU

by joyaries



Category: Haikyuu!!
Genre: Alpha/Beta/Omega Dynamics, Alpha/Omega, Aobajousai, Inarizaki, Karasuno, M/M, Multi, Omega Verse
Language: English
Status: In-Progress
Published: 2020-11-03
Updated: 2020-11-07
Packaged: 2021-03-09 01:33:33
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 3,122
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27366616
Author URL: https://archiveofourown.org/users/joyaries/pseuds/joyaries
Summary: Atsumu came back from oversea to take over his dad's company. Being the inheritor with high position getting him into everyone's high expectations. He, too, himself is seeking for high value to match his status, egoist as much. He seek for a dominant omega as his mate and it has to be a five-star quality omega. Osamu suggests Atsumu to join a club where there are many rich kids joined, it is to help him to link with great 'connections' for business purposes and also to find the perfect mate. Atsumu agreed and he find himself a new rival from the club, the one who has been taking alot of attentions and overshadowed some people - Hinata Shoyo. It irritates him to see the little guy, who are surprisingly a dom alpha despite being small in size getting all the attention by himself. He plan on kicking out that guy, and he surely will, he is the Atsumu Miya - the greatest dom alpha of all time (he says). Meanwhile in the other hand, Oikawa Tooru, a dom omega who joined the club because of his father's demand to seek for best dom alpha mate, always isolate himself in the corner of the club room until he meet the Hinata Shoyo.
Relationships: Hinata Shouyou & Miya Atsumu, Hinata Shouyou & Oikawa Tooru, Hinata Shouyou/Miya Atsumu, Hinata Shouyou/Miya Atsumu/Oikawa Tooru, Hinata Shouyou/Oikawa Tooru
Comments: 6
Kudos: 27





	1. Chapter 1

**Author's Note:**

> hello, i'm back with new story! i have been investing myself to do research on this rare dynamic and told myself why not doing it for my recent top ship? if you're new to my story, i have another one called Throne, mind to check them out as well (it's a mafia haikyuu au). anyway, please don't skip the first chapter as it explain what's sigma, okay?~

Hi, this is Joy. Before we go to the story, I want to explain about this rare dynamic called Sigma. You rarely seen this in most omegaverse stories, not even as side characters. Below I will explain in bullet form, most explanation are from my own research in which are explained by others and mix of my own headcanons.

Please note that sigma is still new to most people in omegaverse, since they were only known for being archetype before this, so my explanations below of sigma headcanons are unofficial and it can be vary. After doing many research, some people have little differences in their sigma headcanons, so I will only collect those headcanons that are the same and add mine to suit the story.

[ also shout-out to user wild-world-of-omegaverse from tumblr, i used their sigma hcs alot because they have better enlightenment about sigma than others that i have read ]

Sigma ;

• hierarchy : in most platforms you can see that sigma stands at the same level as alpha, or maybe higher than alpha. it is because of they have so many similiraties with alpha, that they were always mistaken as one. no one will know unless they're being told. sigmas are also known being alpha with 'lone wolf' personality. unlike alpha who stand for their status and like to lead their packs, sigma prefer to step out from the hierarchy and not follow the law of the hierarchy. they don't like to control or being controlled.

• appearance : they can differ and have the most diversity in body type, but, the most common body types usually fall into shorter but bigger build, or taller and smaller build. as for their canine expression they have lower canines that are incredibly sharp. (meanwhile alphas have sharp upper canines)

• strength : they are as strong as most alphas, are stronger when they have ruts

• pheromone : their pheromone can weaken the alphas, calming the betas & weaken/arouse omega. when they're annoyed/irritated, they naturally let out strong pheromone so they usually avoid crowd to not cause trouble for others

• scent : sigmas have spicier scents and there are times it can be too intense and potent especially during mood downfall.

• voice : the particular voice sigmas have differ from alphas because it release fear in alphas and release calming yet energizing hormones in betas, but has the same effect on omegas as alphas voice would have for them (omegas) which is arousal or dopamine in most situations. 

• heat : sigma went through heat . unlike omega, sigma have no idea when their heat will come since their body don't usually act up before the heat week. when sigma is on heat, they're as weak as omega and they attract alphas, betas and even omegas to them. so when it is heat month they usually will stock up so many food, compile their favourite stuffs to their dens (nest for omegas). they'll disappear from the public to avoid any harm. sigma can die if they hold themselves from being mated for too long because the pain just getting worse everytime their heat come. their heat usually last for 4 days

• rut : sigma also went through rut. they usually have rut in a month then heat on the next month, and it continues on like that. during rut, their hormones are higher than alpha's, which make them stronger and crazily aggresive. unlike alpha who usually have rut when they are close to omega on heat, sigmas' ruts just like heat week. they also lock up themselves during rut time. during rut they release pheromone that can make any omegas near them want them so bad. the pheromone will take over the omegas' senses and they'll act as if they're in heat and in need of alphas. it is not impossible that they can activate omega's heat, but it's a very rare case.

• impregnate : sigmas can impregnate omegas and their children are most likely will be born omegas, but it's also possible to get baby sigma.

• pregnant : they can get pregnant if they're knotted by alphas, betas or omegas.most of the time their children will follow their non-sigma parent's gender, especially alpha and beta.

• mate : unlike alpha-omega, sigmas can be mated by more than a person. they can be mated and knotted by two people at the same time (there are scientific explanation about this but i can't remember and can't understand it since im not a science/bio student ;-; ). they usually give birth quicker than omega, which is three to five months. if they’re mated to an omega they’re more likely to have ruts more often than heats and more heats if mated to an alpha. 

• social : although most sigmas are introverted, they're actually good at carrying conversation, only to those they trust/want. 

• temperament : they are ready to fight whoever belittle them or their friends/loved ones even if they are against gang of dom alphas. their wrath can activate their ruts but it won't be as strong as those they naturally have, but it is more than enough to fight alone. they have habits of bringing various types of suppressants, repellent and other medications for themselves since they're very sensitive with many things and things usually occur during unexpected time for them. 

additional points ;  
• have a great intuition that can help them living on their own to avoid danger but make wise choices in social or educational situations.

• have the best eyes to look out for danger and for resources. 

• sigmas have their own “sigma voice” unique to them .it sounds similar to a lion’s growl that releases fear hormones in alphas, happiness/dopamine in betas, and has a varied reaction in omegas that’s either fear or arousal depending on who they are. 

• up to 90% are introverts making a social sigma rare altogether, but it isn’t impossible.

• sigmas are sometimes confused to be meek or shy when they have the typical quiet nature but anyone who thinks this and try to take advantage of it will learn real quick that they couldn’t be more wrong. 

• sigmas are also rumored to be even better leader figure than alphas if they choose to take up the role as one, a rare thing, but still possible.

• when a sigma is involved with a pack it’s usually because the littermate they’re closest to or their own mate is in the pack or it’s just the entirety of this group is their familial pack. 

• they’re the overseers and advisors who help to guide those around them and make sure the order of things is working out. because they’re the most affected by them after all. 

• sigmas are the most impacted by other dynamic’s scents causing them to sometimes be very intense people, or loners depending on how well they can control themselves or how strong their scent diffuser meds are.

• if a sigma is mated to an omega, since sigmas are the most affected by pheromones, the increase in omega scents will cause them to get more ruts than heats causing their bodily strength to stay up than fluctuating like normal. vice versa if it's alpha-sigma mate

• since sigmas are the most affected by scents causing them to be very aware of their surroundings and have something similar to an omega’s memory. they can be very perceptive to the situation that they’re in and most will use it to their advantage if needed. which brings around the negative concept or rumor that sigmas are manipulative. 

Please leave any questions below regarding sigmas, just in case I miss the important points/details here and there, I will edit and update this chapter to answer the questions! Have fun reading~


	2. First Encounter

**Summary for the Chapter:**

> It's Atsumu's first day of becoming a member of the Glory Club, a club specified in having people socialize and find their true mates and connecting people for future businesses.

**Notes for the Chapter:**

> Main characters age :
> 
> Hinata 24  
> Atsumu 25  
> Oikawa 26

"Please meet our new club member, also the twin of our honored member Osamu-kun, Miya Atsumu." Shirabu introduces Atsumu to the whole club members. The crowd begin to clap, welcoming Atsumu to the club. After greeting some of the members, Atsumu quickly find his brother. Osamu is taken away from his circle and getting dragged to the corner of the club room.

"What theㅡ"

"Do they not taking any suppressant? Ughh its suffocating me." being born as a definite dominant alpha, Atsumu can't help but to be extra sensitive with the scents. The overlapping scents are too strong, it is disturbing.

"Come on, you were the one who asked for my help to search for a perfect dominant omega for you. This is it. The club where we find future connection, future 'mate'. I've been here for months, you'll handle the scents well soon. It is quite overwhelming at first." Osamu chuckles, leaning on the wall. Atsumu sighs, can not believe that he is stucked in the crowd. It's not the people that are too crowded, but the scents. Most people in the club seem to be releasing their scents to show off their dominance, how strong they are. Ofcourse, the dominant alphas are the one that having the outstanding scents among all the members. 

"Can I stop them? I don't mind using my scent to the max if that can stop these bastards. This is not a fucking mating match, for fuck sake!" Atsumu nags, facepalming himself. Osamu pats his twin's shoulder.

"You know the consequences if you do that for this, right?" with a sly grin, Osamu reminds Atsumu to control himself. Being born as twin, both of them always fight to be the strongest. As they grew up, Osamu knew and accepted the fact that Atsumu is an alpha with stronger characteristics. To him, his brother is born gifted. He can quickly catch up with everything that he's lacking. As for Osamu, it's not like he's not strong at all, he have strength in other fields. Although it's not as obvious or as something that can be shown off, but he's grateful for whatever he has now. Atleast, he still thinks he's the winner when it comes to their looks. 

"So, what do you usually do in this club?" Atsumu shifts his eyes to Osamu, not taking any interest to the crowd. He hopes that he can ignore the scents as soon as possible before he going mad. It's not that he's sick of crowded place, but the scents are just too much. 

"Hmm? Well, socializing? This is richy kids club, to be exact. They sometimes manage some party or events. I haven't join any of them. I heard they're planning on having 3 days party on a cruise soon. Since you are here, wanna join?" Osamu takes a glass of wine from a butler who suddenly pop out of nowhere and offer them some drinks. Atsumu's body suddenly shivers, as if there was a cold breeze blew behind him. His eyes quickly glances to the butler kid, who seems attracting others female omegas and some alphas to him. His eyes narrowing, a natural irritation comes whenever he sees someone getting too much attention. Osamu turns his head to look at what makes Atsumu frown and he chuckles. Another win for him, he's more mature than Atsumu, that's what he thinks.

"Who's that? Looks like a popular boy, huh?" Atsumu points to the orange-haired butler.

"Hinata Shoyo, an alpha. Not look like one, but he's a dom alpha." says Osamu simply.

"Didn't you smell it? His scent, it's different. Totally different!" Atsumu had his eyes on Hinata and not even want to atleast cover himself from being obvious. Atsumu thought for some seconds that the scent was rather spicier than normal alpha's scent.

"Hurmm? No, I think. Maybe you're just being extra sensitive? What? Anyways, this wine tastes nice, not bad. I shall ask the name from Wakatoshi-kun later." Osamu takes another sip from the glass. Atsumu stares at Hinata, as if he's hoping for the latter to realize it. 

Hinata, from the other side of the room, actually does realize someone is staring at him but he can't be sure who's it. The crowd of females approaching him is not helping at all. Although he's used to it, but he's not here as the member of the club. He's a butler. He isn't from the wealthy family. He works here to pay for the academy he's in, and for paying rent and other stuffs as well. But somehow, since he started to work here, he's getting all the attention. Maybe not all, but quite alot. In that kind of situation, it is expected that there will be some alphas having grudge on him. Dead threat is nothing uncommon, he even got into a gang fight. His friends told him to quit but this is the only job that pay the highest. $30 per hour, hell yea! Fighting others with his willpower is not a problem, not at all. But living in untruth is the problem.

He IS NOT an alpha. 

And to make it worse, he was born as a rare dynamic of all, a dynamic that people nowadays thought it was extinct.

He is a **SIGMA**.

ㅡ

Shoyo's POV

It's almost 3 hours, my work will end soon. Today I will get my pay! Nothing can beat the happiness that came from getting your salary, that applied in most case. 

"Hinata~ You look great today? Did you perm your hair?" Lev, a dom alpha who I remember he joined the club since a week ago, suddenly came and ruffles my hair. The heck? I politely take a step back. 

"Ah no no. I didn't. I was rushing this morning and forgot to comb my hair after I dried it." I said, but that makes the other girls praise me more, saying that my natural curly hair is a solid charm of mine. Are these omegas crazy? I have never believe them since Suga-san, my supervisor told me that the omegas here are all sugar-coating their words to attract alphas. It is not them to be blamed, though. The hierarchy for the second gender is very cruel, so I kinda understand why some of them are desperate to find a great mate. The problem is, I'm not on their level. Somehow I regret *trading myself to be an alpha, it was useful during childhood, but not now. Not when you're an adult and finding a long-life partner is the top priority.

_*when sigmas were kid and able to understand about their second gender, their parent will do a meeting with the whole family members to do a trade. a trade is when you choose your second gender for the public. the options are only alpha and omega. after trading, the child will begin to study and familiarize themselves with their choice for two weeks, before they privately take a gender test at the hospital. since sigma is believed to be extinct, there is no data about sigma in any hospital, so the technology machine used for the gender test will choose the major points to give out result. ( hinata chose dom-alpha. after two weeks, he went to do a gender test and the result was all pointing to his dom-alpha characteristics. that's how he is known for being a dom-alpha )_

"Hinata, are you okay? You look tired. Eh waiㅡ which one of you are in heat? What the hell get out from here, now!" Kogane who just passed by some people that are crowding me, smelled the sweet scents. Everyone look confused and carefully distancing each other. And I just realized that I'm getting weak all of sudden. My head is spinning and somehow it's getting hot in here? Or is it just my body?

Fuck.

I forgot.

This month is my heat month!

"Ko-Kogane! Please tell Suga-san I'm leaving early. I just remember that Na-natsu told me she's in heat this week and I need to take care of her, so I need to go now. Bye!" quickly, I sprint and squeezed myself between the crowd to leave the clubroom. Fuck, I really fucked up.

I run into the staff room, where my bag is supposed to be. Desperately I open the pouch from my bag to get my heat suppressant.

"Quick, quick. Before anyone comes," my eyes keep looking at the door, but my hands can't seem to grab the important thing. I glance to my pouch.

Double fuck.

HELL NOOOOOOOOOOOO!!!!!

I forgot to refill my pouch with the heat suppressant. Shit! What am I supposed to do?! I can't breathe properly. I need to leave this place as soon as possible. If I'm trapped with anyone, worse that it is with an alpha, I am doom. I'm totally doom.

I threw my pouch inside the bag, quickly zip it and ready to leave. This is totally a super unlucky day for me. If I can make a category for it, this day will win by default. I'm in heat, I forgot to refill my suppressant and now I need to use the stairs from floor 17 to go to the lobby. I can't use the elevator, nope, that's hella dangerous. Anything can happen in that small moving space. 

Thank god that I'm fast, or else I might attract some people from different floor to the stairways. Almost reaching the lobby, almost believing that being fast is beneficial at this moment, I tripped my feet and fall on someone who's on the way. 

"Arghh fuck!" the person below me rub his head after hitting the wall. Strange, my body becomes hotter and I'm turned on. He's an alpha. A dominant one. 

"Huh?! You are the butler from theㅡ" the guy below me quickly cup his mouth and push me. I want an alpha, so bad. Without realizing, I started to point out the good features of the blond guy infront of me.

His hair is silky blond, stylized as undercut. His eyes are shining with striking yellowish hazel in color. His nose is perfectly shaped and his mouth, the lower part is thicker. I want him, my body wants him. I can sense his pheromone. He wants me too, right?

"Fuck! Are you the one releasing this pheromone? This is too strong. Stay away from me!" The blond guy tried to stand up, but his legs became wobbly. I knew that, I did that. My pheromone did that. I can't control anymore, I want him to fuck me right now.

Hinata!

Wake up!

Fight this heat!

You can't let anyone find out about you!

The voice inside my head begin to knock a sense in me. I grab the steel handle of the stair, hardly trying to stand up. I need to leave this place. God please!

"Itㅡit wasn't me. I'm affected too." there, I guess that's enough, right? I push myself to walk downstairs, just a few floors to the lobby. I can make it. 

(end of Hinata's POV)

**Author's Note:**

> follow me on twitter @joyaries_  
> i usually tweet haikyuu ships ideas/headcanons/aus etc~💖


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